Comparison of meteor radar and satellite winds in the Brazilian equatorial region

Abstract

Using data collected from a meteor radar deployed at São João do Cariri (7.4° S, 36.5° W) and from the TIMED Doppler Interferometer (TIDI) on board the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite for 2006, comparisons of horizontal winds (meridional and zonal components) were made in order to evaluate the above-mentioned techniques for scientific investigations and to point out the advantages of each instrument. A grid of ± 5° latitude and longitude centered at São João do Cariri was used to calculate the mean winds from the TIDI, which has a resolution of 2.5 km, starting from 82.5 km and going up to 102.5 km altitude. Otherwise, the meteor radar winds were computed for seven layers of 4 km, each overlapping 0.5 km above and below, which produces layers spaced 3 km apart from 81 to 99 km altitude. When almost simultaneous measurements were compared, substantial discrepancies were observed in the vertical wind profiles. This happened because the meteor radar uses a 1 h bin size to estimate the wind from the echoes detected in the whole sky. On the other hand, the TIDI measures quasi-instantaneous winds from the airglow emissions of a small region. In contrast, when the longer period of observation was taken into account, the temporal meteor radar wind variations throughout the day, averaged over all months, were smoothed and showed more clearly the characteristics of the propagation of tides. The responses of the horizontal wind to the intraseasonal, semi-annual and annual oscillations were satisfactory for both techniques.